1. Field of the Invention
The present invention pertains to a quick release coupling device mainly for use in a marine loading arm installation which is particularly designed to transfer very low temperature fluid products such as liquefied natural gases.
2. Prior Art
A marine loading arm installation is conventionally employed for unloading petroleum products from a tank vessel to a storage tank on land or for loading the same from the storage tank to the tank vessel. The loading arm installation includes an assembly of articulated pipe sections carrying a flanged end connector and is mounted on a sea berth for bolted connection of the end connector to a similar flanged connector on the manifold of the tank vessel. During the transfer of the fluid cargo, the vessel moves due to wind, tide or wave, and the level of the deck thereof changes. Then, the pivotal arms of the loading arm installation can move following the movement of the vessel. However, an excessive movement of the vessel may cause the intervening space between the vessel and the sea berth to exceed the safety reach of the loading arm. In such a case, since the bolted connection of the loading arm to the manifold is unyielding, one of the pipe sections or other parts of the loading arm will break. Consequently, in the conventional loading arm, in order to prevent the breakage and a serious hazard in that case, a quick release coupling device is provided for the flanged pipe connections of the loading arm and the manifold of the tank vessel.
A prior art quick release coupling device includes a plurality of clamping members disposed to straddle the end flanges of two pipes to be coupled, a plurality of connecting rods hinged at their ends to respective pairs of clamping members so as to form an articulated succession of the clamping members, the clamping members and the connecting rods being disposed about the end flanges in the form of a ring provided with a gap between two end clamping members thereof, and connecting means for releasably coupling the two end clamping members to complete the ring. In the coupling device of this type, the connecting means works to release the two end clamping members and hence the plurality of the clamping members from the end flanges in case of emergency.
However, when very low temperature fluid cargo such as liquefied natural gas is transferred through the loading arm installation, a layer of ice forms on the outside of the quick release device. In such a case, even though the connecting means might work in emergency, it is possible that the ice formed on the clamping members prevents them from being released from the end flanges and uncoupling of the loading arm cannot be effected.